On the Formation of Trapped Electron Radiation Belts at Ganymede

Abstract This study presents evidence of stably trapped electrons at Jupiter's moon Ganymede. We model energetic electron pitch angle distributions and compare them to observations from the Galileo Energetic Particle Detector to identify signatures of trapped particles during the G28 encounter. We trace electron trajectories to show that they enter Ganymede's mini‐magnetospheric environment, become trapped, and drift around the moon for up to 30 min, in some cases stably orbiting the moon multiple times. Conservation of the first adiabatic invariant partially contributes to energy changes throughout the electrons' orbits, with additional acceleration driven by local electric fields, before they return to Jupiter's magnetosphere or impact the surface. These trapped particles manifest as an electron population with an enhanced flux compared to elsewhere within the mini‐magnetosphere that are detectable by future spacecraft.